1. Field of the Invention
The present invention relates to compressors driven by an electric motor as the drive source and methods for lubricating the same.
2. Description of Related Art
Japanese Laid-open Patent Publication No. 5-313156 discloses a general scroll compressor that is used as a rotary compressor for an air conditioner, refrigerator, or the like. This scroll compressor is configured such that a movable scroll rotates or orbits relative to a fixed scroll in order to compress a refrigerant to a high pressure within a compression chamber defined between the fixed scroll and the movable scroll. The compressed refrigerant is then discharged from a discharge port defined in the fixed scroll.
In such a scroll compressor, a bearing mechanism for rotatably supporting the drive shaft is conventionally installed on the back of the movable scroll. The bearing mechanism can be lubricated, for example, by supplying lubricating oil to this bearing mechanism. However, Japanese Laid-open Patent Publication No. 5-313156 does not suggest any specific technique for supplying lubricating oil to the bearing mechanism.
Therefore, one object of the present teachings is to provide improved electrically driven compressors that can efficiently lubricate the compressor, including drive shaft bearings disposed therein, using lubricating oil and lubrication methods therefor.
In one of the aspect of the present teachings, electrically driven compressors are taught that utilize pressure difference within a refrigerant channel, which pressure difference occurs between the discharge side and the drive shaft bearing during operation, for circulating lubricating oil to the bearing.
According to another aspect of the present teachings, electric compressors may include a compression mechanism for compressing the refrigerant. A drive shaft is coupled to the compression mechanism and the drive shaft is rotatably driven by an electric motor. Therefore, when the electric motor is activated, the introduced refrigerant is compressed to a high pressure by the compression mechanism and the compressed refrigerant is then discharged. The compression mechanism may comprise, for example, a scroll compressor that compresses the refrigerant by rotating a movable scroll relative to a fixed scroll, a reciprocal compressor that compresses the refrigerant by reciprocating a piston inside a cylinder bore, or other compressor designs.
A motor chamber houses (encloses) the electric motor and is preferably almost completely sealed. This motor chamber may be connected via a communication path to a refrigerant flow channel, which refrigerant flow channel leads from the refrigerant suction port of the compressor to the refrigerant discharge port of the compressor. Consequently, a portion of the refrigerant moving through the refrigerant flow channel reaches a so-called xe2x80x9cstagnated statexe2x80x9d within the motor chamber. Moreover, if a pressure difference exists between the refrigerant flow channel and the motor chamber, the refrigerant will move so as to equalize the pressure difference. In this case, heat transfer occurs between the refrigerant within the refrigerant flow channel and the refrigerant within the motor chamber, thereby cooling the electric motor disposed inside the motor chamber. During this process, the amount of refrigerant that serves to cool the electric motor is only a small portion of the total amount of refrigerant that is moving through the refrigerant flow channel. Thus, this technique has little effect on the compression work being performed by the compressor.
The compressors may further include a lubricating oil supply route and a lubricating oil transfer route. Using the pressure difference within the compressor, the lubricating oil may be supplied via the lubricating oil supply route from the discharge region, e.g., lubricating oil that has been separated from the compressed refrigerant using an oil separator, to the area proximal to the drive shaft bearing (hereinafter also referred to as the xe2x80x9cbearing mechanism regionxe2x80x9d). Because the pressure of the lubricating oil within the discharged refrigerant is higher than the pressure within the area proximal to the drive shaft bearing, by providing a route that connects the discharge region to the bearing mechanism region, the lubricating oil within the discharged refrigerant can be easily supplied to the bearing mechanism using the pressure difference. The lubricating oil supplied to the bearing mechanism (drive shaft bearing) then lubricates the bearing mechanism. When the lubricating oil is being supplied to the bearing mechanism, a portion of the discharged refrigerant may move to the bearing mechanism together with the lubricating oil, thereby raising the pressure at the bearing mechanism region.
The lubricating oil transfer route is a route or path for transferring the lubricating oil that has been supplied to the bearing mechanism region, to the suction-side region using the pressure difference. The lubricating oil transfer route is preferably formed in the portion of the housing that separates an oil storage area on the motor chamber side from the suction-side region. The discharged refrigerant that enters the bearing mechanism region via the lubricating oil supply route together with the lubricating oil pressurizes the bearing mechanism region. Consequently, a pressure difference occurs between the bearing mechanism region and the suction-side region of the compressor. Therefore, by connecting the bearing mechanism region to the portion of the suction-side region that has a lower pressure than the bearing mechanism via the lubricating oil transfer route, the lubricating oil disposed in the bearing mechanism region is easily transferred to the suction-side region of the compressor based on the pressure difference.
The xe2x80x9csuction-side regionxe2x80x9d referred to herein includes the suction region immediately in front of the location where the introduced refrigerant is guided into the compression mechanism, as well as, e.g., a compression chamber, etc. used for compressing the introduced refrigerant in a scroll compressor. That is, the bearing mechanism region can be connected to the low-pressure side of the compression chamber (a location that has a lower pressure than the bearing mechanism region) by means of the lubricating oil transfer route. The lubricating oil thus transferred to the suction-side region via the lubricating oil transfer route is returned to the suction-side region by the compression action of the compression mechanism. In other words, this lubricating oil is discharged from the compression mechanism together with the discharged refrigerant. The lubricating oil in this discharge-side region is supplied to the bearing mechanism again via the lubricating oil supply route. The lubricating oil in the discharge-side region is circulated via the lubricating oil supply route and lubricating oil transfer route, both of which may have relatively simple configurations. Therefore, such compressors are efficient because the lubricating oil contained in the refrigerant can be effectively circulated to lubricate moving parts within the compressor. Moreover, the lubricating oil can be easily circulated using pressure differences of the refrigerant within the compressor.
In another aspect of the present teachings, compressor may include an oil storage area for storing the lubricating oil that has been transferred to the bearing mechanism region via the lubricating oil supply route. In other words, this oil storage area may be a region or space for storing the lubricating oil that has been used to lubricate the bearing mechanism or the excess lubricating oil that has been supplied to the bearing mechanism. This oil storage area preferably may be provided, e.g., on the bottom of the motor chamber. In that case, the lubricating oil that has fallen from the bearing mechanism toward the bottom of the motor chamber due to gravity can be stored in the oil storage area, which may have a relatively simple configuration. Furthermore, the lubricating oil that has been stored in the oil storage area can be reliably transferred to the suction-side region via the lubricating oil transfer route. Therefore, the lubricating oil can be reliably circulated using a relatively simple configuration.
In another aspect of the present teachings, methods are taught for circulating lubricating oil through an electrically driven compressor. Such methods may include circulating lubricating oil by supplying the lubricating oil from the discharge-side region of the compressor to the bearing mechanism, then transferring the lubricating oil to the suction-side region of the compressor, and finally returning the lubricating oil to the discharge-side region again. These operations may be all performed using the pressure differences in the refrigerant along the refrigerant flow path or route. Therefore, the lubricating oil can be easily circulated using differences in refrigerant pressure.
Such methods may preferably further include storing the lubricating oil before it is transferred from the bearing mechanism region to the suction-side region. Then, the stored lubricating oil may be transferred from the bearing mechanism region to the suction-side region. Therefore, the lubricating oil can be reliably circulated using such methods.
Additional objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims.